Hello, I found a fix for this problem.
I searched everywhere but didn't find a fix but to use Windowed (Fullscreen).
Here is a full fix:
1: download Custom Resolution Utility (CRU)
2: extract and run CRU.exe
3: delete all unused Resolutions (all Established resolutions, all Standard resolutions)
4: ALSO delete all TV resolutions in Extension blocks (I removed Audio stuff too because I don´t use it)
5: If you have another Monitor connected to the same things for it.
6: run restart64.exe from the same folder (this restarts the driver)
Example:
after doing this I can select 2560x1440 in Fullscreen 
I hope that I helped somebody with this